Objective The aim of this study was to determine accurate and validated z-score equations for the normal values of coronary diameters adjusted with growth changes of the neonates by testing three different time periods.

Methods Echocardiography was performed on 200 healthy neonates at birth, one and six months of ages. Several regression models for the left (LCA) and right coronary artery (RCA) diameters were tested with weight, height, body surface area and aortic annulus diameter. Reliable standards for the coronary artery diameters for healthy newborns by determining z-score equations with appropriate statistical validations were established.

Results The coronary diameters on birth measurements were strongly correlated with birth weight, height, surface area and the diameter of the aortic annulus (Pearson’s R>0.8, all p<0.01). There were significant associations between the mean data of weight, height, body surface area, aortic annulus and the LCA and RCA diameters measurements of study subjects at birth, one and six months of ages (p<0.05).

Conclusion We present a new set of equations for neonatal z-score calculation on the basis of a large number of healthy neonates on three different time period consisting of birth, one and six month of ages. It is clear with this study that the growth in caliber of the coronary arteries is definite and progressive during postnatal time.